From 10d3be569243def8d92ac3722395ef5a59c504e6 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 21 Apr 2016 10:55:23 -0700 Subject: tcp-tso: do not split TSO packets at retransmit time Linux TCP stack painfully segments all TSO/GSO packets before retransmits. This was fine back in the days when TSO/GSO were emerging, with their bugs, but we believe the dark age is over. Keeping big packets in write queues, but also in stack traversal has a lot of benefits. - Less memory overhead, because write queues have less skbs - Less cpu overhead at ACK processing. - Better SACK processing, as lot of studies mentioned how awful linux was at this ;) - Less cpu overhead to send the rtx packets (IP stack traversal, netfilter traversal, drivers...) - Better latencies in presence of losses. - Smaller spikes in fq like packet schedulers, as retransmits are not constrained by TCP Small Queues. 1 % packet losses are common today, and at 100Gbit speeds, this translates to ~80,000 losses per second. Losses are often correlated, and we see many retransmit events leading to 1-MSS train of packets, at the time hosts are already under stress. Signed-off-by: Eric Dumazet Acked-by: Yuchung Cheng Signed-off-by: David S. Miller --- include/net/tcp.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/net/tcp.h') diff --git a/include/net/tcp.h b/include/net/tcp.h index c0ef0544dfcf..7f2553da10d1 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -538,8 +538,8 @@ __u32 cookie_v6_init_sequence(const struct sk_buff *skb, __u16 *mss); void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss, int nonagle); bool tcp_may_send_now(struct sock *sk); -int __tcp_retransmit_skb(struct sock *, struct sk_buff *); -int tcp_retransmit_skb(struct sock *, struct sk_buff *); +int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs); +int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs); void tcp_retransmit_timer(struct sock *sk); void tcp_xmit_retransmit_queue(struct sock *); void tcp_simple_retransmit(struct sock *); -- cgit v1.2.3